This invention relates generally to optical components, and more specifically to optical components in which amplification is provided, for example to compensate for loss resulting from the operation of the component. Particularly, but not exclusively, the invention relates to optical micromirror switching arrays.
Optical communication systems require high speed data, implemented as optical signals, to be switched between ports of a switching device to allow a signal routing function. Typically, the optical signals are carried by optical fibers, which connect to the optical switching device. There are currently a number of methods for achieving the required switching operation.
One solution comprises an electromechanical arrangement, where a signal in an optical fiber A is routed to fiber B by mechanically aligning fiber A with fiber B. This arrangement is bulky and mostly suited only to 1xc3x97N switch configurations.
An alternative solution is to use a hybrid optical switch in which the optical signals are first converted to electrical signals which are switched in a conventional manner. The resulting outputs of the switch are then converted back to optical signals. This adds complexity and expense to the switching operation.
Optical switches are also known in which a control signal is used to vary the path of an optical signal. For example, waveguide-based switches rely on the change of refractive indices in the waveguides under the influence of an external electric field, current or other signal.
Optical switches using an array of mirrors which can be mechanically tilted are also known. Small micromirrors (for example less than 1 mm) are arranged in a line or array, and the incident light signal is deflected by controlling the tilt angle of each micromirror. Mirror type optical switches include digital micromirror devices which tilt each micromirror by electrostatic force, piezoelectric drive micromirror devices which tilt each micromirror by a fine piezoelectric element and electromagnetic devices which rely upon electromagnetic and electrostatic forces.
In a typical micromirror device, a plurality of micromirrors are arranged in an array of Nxc3x97M mirrors. Each micromirror can be controlled and is capable of switching between a first reflection state and a second non-reflection state. The optical signal is routed between an input and a selected output by controlling the reflection state of each mirror.
Switching and routing components are generally lossy, and when these components are used within an optical node of an optical communications system, pre- and/or post-amplifiers are generally provided to offset the loss of the switch. This adds components to the system and therefore adds cost and complexity and there are reliability issues.
It is therefore desirable to integrate amplification into components when possible. one particular application of the invention is to these micromirror optical switch devices, although the invention is also applicable to other devices.
According to a first aspect of the invention, there is provided an optical component comprising a plurality of optical input ports and a plurality of optical output ports, wherein the component comprises:
a substrate arrangement comprising a polymer amplifying medium;
a pump source providing a pump signal for exciting the polymer amplifying medium,
wherein signals passing through the optical component are routed through the polymer amplifying medium.
The component of the invention provides amplification using a polymer amplifying medium which is integrated into the structure of the component. This amplification can then compensate for the loss resulting from the other functions of the component.
The substrate arrangement may be formed from the polymer or it may be coated with it.
For example, the substrate arrangement may comprise a lens through which all optical input signals are routed. Lenses are often required in optical components and coating a lens provides a cost effective way of implementing the invention. Alternatively, the lens may be formed from the polymer amplifying medium. The substrate arrangement may comprise a plurality of lenses, one lens being associated with each input port.
The component may be an optical switching array, and the substrate arrangement may then comprise a plurality of reflectors, for example micro-electromechanical mirrors with each mirror provided with a layer of the polymer amplifying radium. Different mirrors may be provided with different thickness layers so that different amplification can be provided for different paths through the switch.
The component may comprise an optical switching array, comprising a first array of micro-electromechanical switches and a second array of micro-electromechanical switches, and wherein the mirrors in each array are provided with a layer of the polymer amplifying medium.
Alternatively, the component may comprise an optical switching array comprising a first array of micro-electromechanical switches which directs light from the input ports to a mirror surface and a second array of micro-electromechanical switches which directs light from the mirror surface to the output ports, wherein a layer of polymer amplifying medium is provided over the reflective surface which together define the substrate arrangement.
In this configuration of optical switch, a single internal reflector can be provided with the coating.
The invention also provides a method of routing an optical signal using an optical routing component, comprising:
providing the signal from a first input of the component to a reflector;
amplifying the signal by means of a layer of a polymer amplifying medium provided over the reflector;
providing the signal from the reflector to a selected output of the component.
The reflector may comprise a mirror of a micro-electromechanical mirror array.
An alternative method comprises;
providing the signal from a first input to a lens;
amplifying the signal by means of a polymer amplifying medium forming or provided over the lens;
providing the signal from the lens to a reflector;
providing the signal from the reflector to a selected output of the component.